Ultrasonic nebulizer

ABSTRACT

An ultrasonic nebulizer having a transducer at an end of a liquid receiving nebulizer chamber, for generating ultrasonic waves in the liquid in the chamber, which waves are concentrated substantially at the surface of such liquid. The ultrasonic waves cause extremely rapid formation and collapse of cavitities in the liquid which upon encountering the liquid surface produce aerosol adjacent such surface.

United States Patent Harris et al.

ULTRASONIC NEBULIZER Inventors: Raleigh J. Harris; Allan E. Peck,

both of Oakland, Calif.

Assignee: Misto & Gen Equipment Co.,

Oakland, Calif.

Filed: May 19, 1971 Appl. No.: 145,043

Related U.S. Application Data Continuation of Ser. No. 777,986, Nov. 6,1968, which is a continuation of Ser. No. 552,332, Jan. 12, 1966,abandoned.

[56] References Cited UNITED STATES PATENTS 3,387,607 6/1968 Gauthier eta1. 128/173 R Primary Examiner-Williarn E. Kamm Attorney, Agent, orFirm-Townsend and Townsend [57] ABSTRACT An ultrasonic nebulizer havinga transducer at an end of a liquid receiving nebulizer chamber, forgenerating ultrasonic waves in the liquid in the chamber, which wavesare concentrated substantially at the surface of such liquid. Theultrasonic waves cause extremely U.S. Cl. 128/194, 239/338 id f ti andcollapse of Cavitities in the liquid Int. Cl A61m 11/04 which uponencountering the liquid surfac'3 produce Field of Search 128/173, 194;239/102, aerosol adjacent Such Surface- 4 Claims, 7 Drawing Figures 7I401: H07: I 108 85 105 a g 99 {I06 |o4-; 17m? Patented Jan. 21, 1975 73,861,386

2 Sheets-Sheet 1 l 'INVENTORS 7 I3 BY /ALLAN E. PECK RfiLEIGH J. HARRIS26%, 77/9444, Jada MM ATTORNEYS Paiehted Jan. 21, 1975 2 Sheets-Sheet 2INVENTORS ALLAN E. PECK RALEIGH J. HARRIS fi k, aw xww ATTORNEYSULTRASONIC NEBULIZER CROSS-REFERENCE TO RELATED APPLICATION Thisapplication is a continuation of application Ser. No. 777,986, ofRaleigh J. Harris and Allan E. Peck, filed Nov. 6, 1968, which is acontinuation of abandoned application Ser. No. 522,332, of Raleigh J.Harris and Allan E. Peck, filed Jan. 21, 1966.

BACKGROUND OF THE INVENTION This invention relates generally to liquidnebulizing or aerosolizing and more particularly to a nebulizingapparatus in which ultrasonic waves are transmitted through a liquid togenerate an aerosol.

In the treatment of respiratory diseases, techniques are employed whichinvolve the inhalation by the patient of aerosols. Conditionsaccompanying many respiratory diseases are respiratory congestion andinadequate expulsion by the patient of secretions from the lungs, and ithas been found that a water or saline aerosol introduced into the lungsassists in correcting these. It is conventional practice to directlyintroduce a medicine, such as relaxant for the treatment of asthma, intothe respiratory system in aerosol form; and as a diagnostic techniquethe analysis of sputa specimens coughed up after the deposit of aerosolin the lungs provides more representative information than may beobtained from a biopsy.

Conventional nebulizers for aerosol generation utilized in inhalationthereapy include a supply of liquid and a supply of breathable gas underpressure. A liquid discharge nozzle and gas discharge nozzle arearranged so that a stream of the gas is discharged past the dischargingliquid to provide a mixture of gas and nebulized liquid which isbreathed by the patient. This type of nebulizer requires an aircompressor or other source of gas under pressure and is quite limited inits maximum output, which necessitates the use of multiple nebulizersfor higher output applications. Deepest penetration of aerosols into therespiratory system is accomplished with minimum aerosol particle sizeand maximum particle uniformity, and the above described conventionaltype of nebulizers frequently do not pro duce particles of thischaracter.

SUMMARY OF THE INVENTION The above-noted and other disadvantagesassociated with conventional nebulizers are avoided by the use of thenebulizer of the present invention in which aerosol is generated bytransmitting ultrasonic waves through the liquid to be nebulized, suchwaves emanating from an ultrasonically vibrating element acousticallyconnected to the liquid.

Accordingly, it is an object of the present invention to provide anapparatus for generating aerosol from a liquid by means of ultrasonicwaves.

It is another object of this invention to provide an improved nebulizerfor generating aerosols for medical application, at a higher output thanheretofore practically attainable, which aerosols have smaller and moreuniform particle size than heretofore.

It is yet another object of this invention to provide an improvednebulizer in which portions which contact the nebulized liquid are notadversely affected by such contact and are readily sterilizable.

It is a further object of this invention to provide an ultrasonicnebulizer in which nebulization occurs more efficiently than heretofore.

It is a still further object of this invention to provide an improvednebulizer which is effectively prevented from suffering damage when leftin an operating condition for a long period of time with an inadequatesupply of liquid to be nebulized.

An additional object of the invention is to provide a novel vial forliquid medicine for use in an ultrasonic nebulizer and in which ameasured quantity of such medicine may be contained for shipment andstorage.

This invention possesses other objects and features of advantage, whichwith the foregoing, will be set forth in the following description ofpreferred forms of the invention which are illustrated in the drawingsaccompanying and forming part of this specification. It is to beunderstood, however, that variations in the showing made by saiddrawings and description may be adopted within the scope of theinvention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,

FIG. 1 is a perspective view of one form of ultrasonic nebulizerembodying the present invention, showing the major components thereof.

FIG. 2 is a vertical sectional view of the nebulizer assembly of thepresent invention taken substantially along line 2-2 of FIG. 1, and inslightly enlarged scale relative thereto.

FIG. 3 is a side elevational view, partly broken away, of the nebulizerand liquid supply assemblies as seen generally from line 33 of FIG. 1.

FIG. 4 is an enlarged perspective view of the lower portion of thenebulizer assembly of FIG. 1 broken away to illustrate the transducerand transducer mounting structure.

FIG. 5 is an exploded perspective view of the upper portion of thenebulizer assembly of FIG. 1, on an enlarged scale relative thereto, andparticularly illustrating the baffle and baffle enclosure.

FIG. 6 is a side elevational view of a modified form of the lowerportion of the nebulizer assembly of FIG. 1, partly broken away, andenlarged relative thereto, utilizing a vial containing a predeterminedvolume of liquid medicine to be nebulized instead of the liquid supplyassembly of FIGS. 1 and 3.

FIG. 7 is a perspective view of a vial for liquid medicine adapted foruse with the ultrasonic nebulizer of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In detail, a preferredembodiment of the present invention (FIG. 1) comprises three majorcomponents; an ultrasonic wave generator or oscillator l, a nebulizerassembly 2, and a liquid supply reservoir 3.

Oscillator 1 includes a housing 4 in which is a chassis or base 12 forcarrying the electronic components of a conventional ultrasonicgenerator circuit and a blower unit 13. Housing 4 comprises a pair ofside walls 5, 6, top 7, base wall 8 and end wall 9. At the front end ofhousing 4 is a panel 15 which is recessed slightly from the front edgesof walls 5, 6, 7, 8. Chassis l2 and panel 15 are removably secured towalls 5, 6 of housing 4 by screws 16. When panel 15 and chassis 12 aresecured to walls 5, 6 (FIG. 1) the components carried by the chassis arewithin protective housing 4, but are also ventillated through openings11 in said walls. Upon removal of screws 16, panel 15 and chassis 12 maytogether be readily removed through the open end of housing 4 for accessto the enclosed components. Elongated recessed portion 17 at each sideof panel 15 facilitates gripping the panel with the fingers for removalthereof and provides added openings for ventillation.

Rigidly secured to the inside surface of panel 15 proximate each topcorner thereof is a horizontally, laterally, outwardly projecting arm 18(FIG. 1) formed of an inner bar portion 19 riveted or screwed to panel15 and an outer horizontal end ring 22 having a forward section which isvertically slotted as at 23. Arms 18 are provided for mounting nebulizerassembly 2 and liquid supply reservoir 3 hereinafter described indetail, and slots 23 facilitate their mounting as will become clear. Theforward edge of walls 5, 6 are notched at 24, 25 respectively, toaccommodate bar portions 19. Housing 4, chassis l2 and panel 15 may allbe of suitably rigid aluminum sheet material, or other material, notingthat the material of panel 15 must be of sufficient thickness to enablesaid panel to support arms 18 and nebulizer assembly 2 and liquid supplyreservoir 3. Nebulizer assembly 2 (FIGS. 1 and 2) is generally elongatedand cylindrical and at its base has a circular cylindrical cap 26 ofconductive material and including a central axis recess 27, FIG. 2,extending downwardly from the flat upper surface 28 of said cap. A bore29 extends radially from one side of cap 26 to intersect recess 27 andincludes an enlarged outer portion 32 providing an outwardly facingshoulder 33. Received within bores 29, 32 is a conventional electricalcable connector 34, one electrical connection of which is a conductivesheath 35 in bore 29, with an annular flange 36 engaged shoulder 33. Theother electrical connection of connector 34 is a central pin 37insulated from sheath 35 by coaxial insulating layer 38, and withconnector 34 positioned as described, the inner end of pin 37 extends tosubstantially the center of recess 27. Connector 34 is secured withinbores 29, 32 by an allen screw 39 threaded into cap 26 for bearingagainst sheath 35.

A cylindrical cup member 42 (FIGS. 2, 4) formed of a plastic or othernonconductive material rests on upper surface 28 of cap 26 and includesa flat circular base 43 bounded by an upstanding rim 44, with said basehaving a central circular opening 45 extending through a depending boss46 which projects into recess 27 A generally flat circular disc 47 of athin conductive sheet material rests on base 43 and is dimpled centrallyso as to provide a slight projection 48 which extends downwardly throughopening 45. A light compression spring 49 extends vertically between theinner end of pin 37 and disc 47 and is centered in boss 46 by projection48. The length of spring 49 in the extended position is greater than thedistance between pin 37 and disc 47 so that the disc is urged upwardlythereby under relatively slight pressure.

A ring 52 of a conductive material rests on cap 26 in surroundingengagement with cup member 42 and has an inwardly directed annularflange 53, FIG. 2, at its upper end providing a downwardly facingshoulder 54 which overlies the top edge of rim 44 and terminatesradially inwardly of such top edge.

Cap 26, cup member 42, disc 47 and associated structure together providea mounting for a disc transducer 55, such as a piezoelectric ceramiccrystal (FIGS. 2, 4) which is seated on disc 47. Transducer 55 is of thetype which when excited by electrical energy converts the same intomechanical wave energy, and it is therefore suitably resiliently mountedbetween disc 47 which is yieldably urged upwardly by spring 49, and anO-ring 56 of conductive material, disposed peripherally of thetransducer upper surface and partially compressed between said surfaceand shoulder 54.

Radio frequency electrical energy is impressed upon transducer 55through an electrical circuit to one electrical contact at its lowersurface and the other at its upper surface. Such circuit is completedfrom pin 37 through spring 49 and disc 47, all of which are insulatedfrom cap 26, to the underside of transducer 55, and from the upper sideof said transducer through 0- ring 56, ring 52, cap 26 and to the outersheath of connector 34. The two electrical connections of connector 34are electrically connected to the output of ultrasonic oscillator l.

The oscillator wave generator 1 is preferably of the type commonly usedin radio work and capable of producing a tuned, high-powerelectromagnetic wave of radio frequency. For purposes of this invention,generator 1 preferably puts out electromagnetic energy at approximately15 watts to vibrate transducer crystal 55 at 1.4 megacycles.

Housing 4 (FIG. 1) also includes on its front panel 15 and connected inthe wave generator circuit a power switch 109, indicator light 112, fuseholder 113 and the connector 114 to which a power cable 115 isconnected. When switch 109 is moved to the on position, the output ofgenerator 1 is applied to transducer 55 through two-wire cable 115, onewire of which is connected to sheath 35 and the other of which isconnected to pin 37. Switch 109 also activates blower unit 13.

An elongated, cylindrical, open-ended tube 57 (FIG. 2) of plastic orother nonconductive material is formed with a circular recess at itslower end, providing a downwardly directed annular flange 58 and adownwardly facing shoulder 59, which receives the upper end of ring 52.A plurality of screws 62 (only oneof which is shown in FIG. 2) extendingthrough cap 26 and ring 52 into threaded engagement with the bottom endof tube 57 secure the transducer mounting in place. An O-ring seal 64seated in a recess 65 adjacent shoulder 59 is compressed against theupper surface of flange 53 of ring 52 thereby rendering the jointbetween said ring and tube 57 liquid tight.

Above transducer 55, tube 57 provides a chamber in which liquid is to benebulized in the form of a circular central axial bore 67 of the lowerportion of which is the same diameter as the opening bounded by flange53 of ring 52, which is slightly less than the outside diameter oftransducer 55. The upper portion of bore 67 is of substantially largerdiameter providing between said portions and generally centrally of tube57 an upwardly slanting shoulder 68, an upwardly facing horizontalshoulder 72, and a horizontal step 73. Said step positions upper wallportion 74 outwardly of the lower portion of tube 57 and provides anexternal, downwardly directed shoulder 66 for engagement by ring 22(FIGS. 1-3) for supporting the same. A radially inwardly directed flange75 at the upper end of wall portion 74 has a downwardly slanting uppersurface 76, and extends inwardly to the same inside diameter as theinner wall portion above shoulder 72.

A second cylindrical open-ended tube 77, preferably of a transparentplastic or similar transparent material, has an outside diametersubstantially equal to the inside diameter of flange 75 and the wallportion above shoulder 72, and a wall thickness equal to the width ofsaid shoulder. Tube 77 is thus insertable into tube 57 with its outsidesurface in engagement with flange 75 and the wall portion at step 73 andwith its bottom end resting on shoulder 72. When tube 77 is inserted inthis manner, it forms a larger diameter continuation of bore 67 and isof sufficient length to project upwardly from the upper end of outertube 57 to an upper end 78 formed with external threads 79.

Threadedly secured on said upper end 78 and communicating with tube 77is a cylindrical baffle enclosure 82 (FIGS. 2, 5), having for suchpurpose internal threads 83 on its lower end complementary with threads79. A baffle member 84 is received in enclosure 82, and a cap 85 closesthe upper end thereof.

Above the lower threaded portion, the cylindrical wall of enclosure 82includes a relatively thick wall portion 86 extending to the uppersurface of a transverse web 87. A generally radial port 88 in wallportion 86 is directed angularly downwardly toward and communicates withthe interior of enclosure 82.

A vertically extending deflector or baffle plate 89 depends from theunderside of web 87 centrally of enclosure 82 to divide the interior ofsaid enclosure below web 87 and the upper portion of tube 77 into twosubstantially semi-cylindrical portions. The side edges of plate 89 arenotched at 92 (FIG. 5) to receive the inwardly projecting sides of wallportion 86. Plate 89 is secured in position by being wedged against thecurved inner sides of wall portion 86 by screw 94, threaded radiallythrough wall portion 86 into engagement with the surface of said plate.

At the side of plate 89 adjacent port 88, web 87 is provided with arelatively small aperture 95, and at the other side of said platesubstantially all of web 87 is cut away to provide a generallysegmentally-shaped aperture 96 (FIG. 5). The enclosure wall portion 97above web 87 is formed with an internal, upwardly facing shoulder 98spaced upwardly from web 87.

Baffle member 84 (FIGS. 2, 5) includes a central cylindrical body 99,projecting radially from which and equally axially spaced therealong arethree relatively thin segmentally shaped fins 102, each having astraight edge 103 adjacent the periphery of body 99 and a sharpenedcircular edge 104 concentric with said body. The diameter of curvededges 104 of fins 102 is substantially the same as and that ofcylindrical body 99 is approximately one-half of the inside diameter ofwall portion 97 above shoulder 98 so that member 84 fits in enclosure 82with curved edges 104 positioned substantially against wall 97 and thelowermost fin 102 resting on shoulder 98. When baffle member 84 iscorrectly positioned, straight edge 103 of the lowermost fin 102 isparallel with the upper edge of plate 89 and disposed over aperture 95,and the curved portion 104 of said lowermost fin extends in spaced,covering relation to segmental aperture 96. It will be noted that thecurved portion 104 of the central fin 102 is diametrically opposed tothe curved portions of the upper and lower fins, thereby providing atortuous passageway from aperture 96 past baffle member 84 to the upperend of enclosure 82.

Cap fits in sealing relation to the upper end of enclosure 82 by meansof an O-ring 105 received in a recess 106 in the cap. A chamber 107opening downwardly of cap 85 has an inner wall surface convergingupwardly toward and communicating with an upwardly opening centraloutlet port 108. All of the components of the baffle structure arepreferably formed of a plastic or other noncorrodible and sterilizablcmaterial.

A hose 116 is connected at one end to the output of blower 13 in housing4 (FIG. I) and at the other end to a fitting 117 in port 88 (FIG. 2) toconduct an air stream from blower 13 into the upper end of tube 77 onthe side of baffle plate 89 opposite aperture 96.

To obtain aerosol of maximum particle uniformity and optimum nebulizingefficiency with respect to the rate of aerosol generation, it isnecessary to provide a continuous supply of liquid to the interior oftube 57 and to maintain the level of such liquid substantially constant.Liquid to be nebulized is supplied to the inte rior of bore 67 fromsupply reservoir 3 (FIGS. 1 and 3) which includes an inverted jar 119across the bottom open end of which is sealingly secured a closuremember 122 (FIG. 3) by a ring cap 123 threaded onto said bottom end.

An annular gasket 124 is bonded to the periphery of the upper surface ofclosure member 122, and a central, generally circular block 125 (FIGS. 1and 3) depends from the underside thereof and is received in ringportion 22 of the left-hand arm 18. Extending vertically upwardlly fromclosure member 122 into the interior ofjar 119 is an open-ended tube 126bent in the form of an elongated inverted U. One threaded end 127projects through closure member 122 and block 125, is secured thereto bynuts 128, and is open to the atmosphere. The opposite end 129 terminatesinwardly of closure member 122 and is likewise threaded. End 129threadedly receives a hollow sleeve 132 having a threaded axial bore 133and a pair of opposed manually graspable flat surfaces, so that saidsleeve may be readily rotated on end 129 to vary the elevation of thelower open end 139 of sleeve 132 above closure 122. A small threadedopening 134 through closure member 122 and block 125 receives a hosefitting 135. Recesses 136 are formed in block 125 to accommodate fittingand the lower nut 128.

Supply liquid is conducted from reservoir 3 into the interior of bore 67(FIG. 3) through flexible conduit or tube 137 connected at the inlet endto fitting 135 and at the outlet end to a fitting 138 (FIGS. 2, 3) inthe lower portion of tube 57, and is prevented from leaking from theinterior of bore 67 by O-rings 56, 64. Fitting 138 includes a checkvalve to permit flow of liquid one way only, i.e., into the interior ofsaid bore.

The level of liquid in bore 67 is maintained constant as the liquid issupplied thereto, and such level is even with the lower end 139 ofsleeve 132 for reasons presently to be explained. Arms 18 respectivelysupport nebulizer assembly 2 and liquid supply reservoir 3 so thatsleeve 132 is adjustable to be positioned with lower end 139 on a levelwith shoulder 72 of tube 57.

Initially jar 119 is filled with supply liquid and placed on arm 18 sothat the upper surface of said liquid is substantially above sleeve 132.End 139 is in communication with the atmosphere through tube 126, andwhen the liquid system is in static equilibrium the liquid in jar 119 atthe level of sleeve end 139 is at atmospheric pressure, with thepressure of the liquid and air thereabove less than atmospheric and thepressure of the liquid therebelow greater than atmospheric. The liquidsystem initially and continuously seeks a state of static equilibrium inwhich the surface of the liquid in base 67, which surface is always atatmospheric pressure, rises to the level of sleeve end 139. As theliquid in bore 67 is dissipated through nebulization, any tendency forthe surface thereof to drop is resisted since such a drop to below thelevel of sleeve end 139 creates a pressure differential wherein theliquid at end 139, being above the surface of the liquid in bore 67 isat less than atmospheric pressure. To eliminate such differential,liquid is supplied from jar l 19 to the interior of bore 67, whilesimultaneously air is introduced into said jar through tube 126 todisplace the supplied liquid; so that the surface of the liquid in bore67 is maintained at the level of sleeve end 139. When the liquid in jar119 drops below the level of sleeve end 139, the liquid in bore 67 is ata corresponding level.

In operation, the oscillator circuit is initially connected to a currentsource, jar 119 is filled with supply liquid which may be water, salinesolution or other liquid; nebulizer assembly 2 and liquid supplyreservoir 3 are mounted on arms 18, with cable 115, tube 137, connector34 and fitting 138 being passed through slots 23, and the liquid systemtherein permitted to come to a state of equilibrium. Power switch 109 isthen moved to the on position, whereupon ultrasonic oscillation oftransducer 55 by application of electrical energy from generator 1, andactuation of blower unit 13 are initiated. as indicated by illuminationof pilot light 112. By varying the power supplied to transducer 55, theamplitude of oscillation thereof may be regulated to thereby provide oneform of control of the rate of aerosol generation of the nebulizer.

When transducer 55, previously described as a disc of piezoelectriccrystal, is excited by electromechanical energy at ultrasonic frequency,its faces move with respect to each other axially of the disc, i.e.,oscillate, at a corresponding frequency. The amplitude of oscillationproduced by a given amount of incident energy is markedly greater at theresonant frequency of the crystal, and it is therefore preferable todrive the crystal at such resonant frequency, normally indicated as itsrated frequency.

When one of the oscillating faces is in contact with a body of liquid,ultrasonic waves are transmitted therefrom through the liquid. Also, apressure drop in the liquid occurs at the crystal face, which causes theformation and collapse of cavities or bubbles at an extremely high rate.These bubbles stream toward the surface of the liquid and encounter theinterface between the liquid and air, resulting in the production offine mist or aerosol adjacent the liquid surface.

In the present nebulizer aerosol particle size uniformity and rate ofaerosol generation are maximized by concentrating the beam of ultrasonicwaves at the point where it intersects the liquid surface and focusingthe stream of bubbles to a focal point substantially at such liquidsurface. The desired concentration of the ultrasonic beam isaccomplished in a beam concentrating chamber defined by the wall surfaceof bore 67 and the adjacent face of transducer 55, which chamber isfilled with liquid to be nebulized.

Bore 67 is of a uniform diameter from its end adjacent transducer 55 tosubstantially its upper opposite end at which is an enlarged diameterportion. The diameter of the uniform portion of bore 67 is related tothe diameter of transducer 55 and is approximately equal to but slightlyless than such diameter. It is desirable that the bore diameter berelatively small so that the reflective character of the solid materialis utilized to confine and highly concentrate the ultrasonic beam.However, a practical minimum bore diameter should not be significantlyless than that of the transducer since solid material overlying thetransmitting face of the transducer in the path of the transmitted wavesabsorbs a portion of the transmitted energy to decrease nebulizingefficiency, though the nebulizer is not thereby rendered totallyinoperative. In the present nebulizer, peripheral contact between tube57 and transducer 55 is necessary for effecting a liquid tight seal.

After the diameter of the uniform portion of the bore and the resultingfocal point of the convergent bubble stream in the liquid to benebulized are determined, the length of such portion is fixed so thatthe focal point occurs in the enlarged upper portion of the boresubstantially at shoulder 72. This is the optimum level for the liquidin bore 67 and the level at which such liquid is automaticallymaintained in the present nebulizer by supply reservoir 3 and theabove-described liquid level regulating structure.

In the illustrated apparatus, transducer 55 is a disc of piezoelectricceramic, which may be of the barium titanate type, approximatelyseven-eighths inch in diameter, and tube 57 is nylon and formed withbore 67 which has a lower portion of a uniform diameter ofeleven-sixteenths inch along a length of approximately one andfive-eighths inches, and an upper enlarged diameter portion extendingaxially an additional onefourth inch to shoulder 72. When transducer 55is excited at 1.4 megacycles by generator 1 of approximately 15 wattsoutput, optimum aerosol generating efficiency occurs with the liquidsurface substantially on a level with shoulder 72, to generate aerosolat a rate of approximately 2 cc. per minute.

Ultrasonic beams can alternatively be made to converge by utilizing aconcavely curved crystal, but a curved crystal is considerably moreexpensive than a flat one.

When the nebulizer is operating, the liquid in chamber 67 iscontinuously dissipating; but the liquid surface is maintained at theoptimum level until the reserve in supply jar 119 drops below suchlevel. As the liquid in bore 67 drops below this level, the efficiencyof nebulization decreases markedly. In the apparatus illustrated in FIG.2, it requires a period of several hours to exhaust all the liquid bynebulization after the liquid surface drops from the desired level.Therefore, if the apparatus is inadvertently left in an operatingcondition with an inadequate liquid supply, changes are great that thecondition will be discovered and corrected long before all the liquid isexhausted and damage done to the apparatus through overheating.

The air stream from blower unit 13, as indicated by arrow 142 (FIG. 2),carries the aerosol from tube 77 upwardly past baffles 103 which trapout any gross particles and through port 108 and a hose I40 and mask orother suitable conduit to the patient. The stream from blower 13, havinga relatively slight flow rate, discharges from fitting 117, impingesagainst plate 89, passes downwardly along the near face of said plateand around the lower end thereof to pick up the mist generated in bore67, then upwardly with said mist along the opposite face of said plate,and through baffle enclosure 82 and port 108. The flow rate of air fromblower 13 may be regulated as best suits the particular application.Oxygen or other breathable gas under pressure may be utilized as theaerosol carrier instead of the air stream, or the patient may draw theaerosol in by inhalation. In the treatment of particular diseases,specific gas carriers may be called for, but it should be noted thatcompressed gas or an air stream is not essential to the nebulizingprocess.

Aerosol particle size is further reduced to maximize uniformity by theuse of the baffle structure. With the baffle in the instant apparatus,the maximum size of particles discharged from port 108 is under microns.

The aerosol is carried upwardly through aperture 96 and follows atortuous path, indicated by arrow 143 (FIG. 5) along both faces of fins102, then past cham her 107 and through port 108. Particles which areheavier than desired impinge against the underside of fins 103 and otherobstructing surfaces and condense, and the condensation drains alongwall 97 and finally through aperture 95. The lighter particles passthrough the baffle structure without contacting any of the bafflesurface.

Parts of the apparatus which are in contact with the liquid or aerosolare easily separable, e.g., tube 77, member 84 and cap 85 are eachseparable from enclosure 82; and of a sterilizable and non-corrodiblematerial.

If it is desired to administer a relatively small and carefully measureddosage of medicine in aerosol form, the nebulizing apparatus may bemodified as illustrated in FIGS. 6 and 7. In FIG. 7, a vial 144 forliquid medicine which may be utilized in place of tube 77 is shown. Vial144 includes a cylindrical wall 145, of the same diameter as tube 77,having a threaded end on which is screwed a cap 146. The opposite end isclosed by an end wall or diaphragm 147 having a central hemisphericaldepression or bowl 148 projecting axially outwardly therefrom. A label149 or other means is provided for carrying information identifying themedicine and relating to proper dosage, etc. Medicine may thus be storedand transported in vial 144 just as with conventional vials.

With cap 146 removed, vial 144 may be inserted in tube 57 (FIG. 6) withdiaphragm 147 resting on shoulder 72, and baffle enclosure 82 isthreaded onto the upper end thereof in place of said cap. In themodified embodiment, a measured amount of liquid medicine in vial 144 isnebulized rather than liquid in bore 67, so that no continuous liquidsupply is required. Liquid supply assembly 3 is disconnected and,instead, the lower portion of chamber 67 is initially filled with liquidto the level of shoulder 72. If chamber 67 is inadvertently filled aboveshoulder 72, flange 75 prevents spillage of the displaced liquid whenvial 144 is inserted.

With vial 144 in place, the liquid in chamber 67 below wall 147 issubstantially sealed in such space so that it cannot be nebulized; andwithin the vial there is, 6

pressed upon diaphragm 147, causing said diaphragm to vibrateultrasonically. Vibrations impinging on rounded depression 148 arefocused thereby a small fraction of an inch above diaphragm 147 so thatthe focal point occurs substantially on a level with the upper surfaceof the medicine. Projection 148 accomplishes sufficient focusing of theultrasonic waves so that the medicine will continue to be rapidlynebulized as it is dissipated until it is completely exhausted. Themedicinal aerosol may be carried by air or other breathable gas in themanner previously described.

We claim:

1. A nebulizer, comprising:

a. a generally vertically elongated nebulizer chamber having a closedbottom end and an outlet at its upper end, for receiving therein liquidwith the upper surface of said liquid a predetermined level above saidbottom end;

b. an electromechanical transducer supported at said bottom end with asurface thereof acoustically connected to the liquid in said chamber;

c. means for exciting said transducer for causing it to generateultrasonic waves; and

. means defining an ultrasonic beam concentrating chamber forconcentrating said waves at said predetermined leve] including a portionof said nebulizer chamber of substantially circular interiorcross-section extending vertically from said transducer substantially tosaid predetermined level, said interior cross-section being of uniformdiameter between points immediately above said transducer andimmediately below said predetermined level, the distance between saidpoints being at least twice the length of said uniform diameter.

2. A nebulizer comprising:

a. a generally vertically elongated nebulizer chamber having a closedbottom end and an outlet at its upper end, for receiving therein liquidwith the upper surface of said liquid a predetermined level above saidbottom end;

b. an electromechanical transducer of generally fiat form supported atsaid bottom end and including a planar surface acoustically connected tothe liquid in said chamber;

c. means for exciting said transducer for causing it to generateultrasonic waves; and

d. means for concentrating said waves at said predetermined levelincluding a portion of said nebulizer chamber of substantially circularinterior crosssection extending vertically from said transducersubstantially to said predetermined level, said interior cross-sectionbeing of uniform diameter between points immediately above said planarsurface of said transducer and immediately below said predeterminedlevel, the distance between said points being'at least twice the lengthof said uniform diameter.

3. The nebulizer of claim 2, including:

e. a separable, elongated vial for liquid insertable into the upper endof said chamber with a bottom wall substantially at said predeterminedlevel;

f. said bottom wall including a downwardly extending central depressioncurved for concentrating said waves at substantially said bottom walland upper surface of the liquid in said vial.

4. In a device for ultrasonic nebulization of liquid, in-

cluding a generally vertically elongated nebulizer lar interiorcross-section extending from said planar surface substantially to saidpredetermined level, said interior cross-section being of uniformdiameter between points immediately above said planar surface of saidtransducer and immediately below said predetermined level, said pointsbeing spaced apart a distance at least twice the length of said uniformdiameter.

1. A nebulizer, comprising: a. a generally vertically elongatednebulizer chamber having a closed bottom end and an outlet at its upperend, for receiving therein liquid with the upper surface of said liquida predetermined level above said bottom end; b. an electromechanicaltransducer supported at said bottom end with a surface thereofacoustically connected to the liquid in said chamber; c. means forexciting said transducer for causing it to generate ultrasonic waves;and d. means defining an ultrasonic beam concentrating chamber forconcentrating said waves at said predetermined level including a portionof said nebulizer chamber of substantially circular interiorcross-section extending vertically from said transducer substantially tosaid predetermined level, said interior cross-section being of uniformdiameter between points immediately above said transducer andimmediately below said predetermined level, the distance between saidpoints being at least twice the length of said uniform diameter.
 2. Anebulizer comprising: a. a generally vertically elongated nebulizerchamber having a closed bottom end and an outlet at its upper end, forreceiving therein liquid with the upper surface of said liquid apredetermined level above said bottom end; b. an electromechanicaltransducer of generally flat form supported at said bottom end andincluding a planar surface acoustically connected to the liquid in saidchamber; c. means for exciting said transducer for causing it togenerate ultrasonic waves; and d. means for concentrating said waves atsaid predetermined level including a portion of said nebulizer chamberof substantially circular interior cross-section extending verticallyfrom said transducer substantially to said predetermined level, saidinterior cross-section being of uniform diameter between pointsimmediately above said planar surface of said transducer and immediatelybelow said predetermined level, the distance between said points beingat least twice the length of said uniform diameter.
 3. The nebulizer ofclaim 2, including: e. a separable, elongated vial for liquid insertableinto the upper end of said chamber with a bottom wall substantially atsaid predetermined level; f. said bottom wall including a downwardlyextending central depression curved for concentrating said waves atsubstantially said bottom wall and upper surface of the liquid in saidvial.
 4. In a device for ultrasonic nebulization of liquid, including agenerally vertically elongated nebulizer chamber having a closed bottomend and an outlet at its upper end, receiving therein said liquid withan upper surface a predetermined level above said bottom end, agenerally flat electromechanical transducer at said bottom end having aplanar surface in acoustical contact with said liquid and means forcausing said transducer to generate ultrasonic waves in said liquid,means for concentrating said waves at said predetermined level,comprising: a. a nebulizer chamber portion of substantially circularinterior cross-section extending from said planar surface substantiallyto said predetermined level, said interior crosssection being of uniformdiameter between points immediately above said planar surface of saidtransducer and immediately below said predetermined level, said pointsbeing spaced apart a distance at least twice the length of said uniformdiameter.